effetto dissolvenza su testo

[Ashry]

Salve a tutti, sto cercando di chreare una sorta di newsticker con effetto dissolvenza su testo ma non so perchè non riesco a farlo funzionare

import flash.net.URLRequest;
import flash.text.TextField;
import flash.text.TextFieldAutoSize;
import fl.transitions.Tween;
import fl.transitions.easing.*;
import fl.transitions.TweenEvent;


stop();
var my_speed:Number = 2;
var my_total:Number;
var allNews:XMLList;
var my_url:String;
var my_title:String;
var my_date:String;

var sfondo:bg_mc = new bg_mc();

addChild(sfondo);

var my_labels_array:Array = [];
var my_counter:Number = 0;
var my_playback_counter:Number = 0;

var my_newsTicker:Sprite = new Sprite();
var my_labels_slides:Sprite = new Sprite();

var my_timer:Timer;
var my_prev_tween:Tween;

var xmlLoader:URLLoader = new URLLoader();
var xmlData:XML = new XML();

xmlLoader.load(new URLRequest("../news.xml"));

xmlLoader.addEventListener(Event.COMPLETE, LoadXML);


function LoadXML(e:Event):void {
    xmlData = new XML(e.target.data);
    ParseNews(xmlData);
}

function ParseNews(newsInput:XML):void {
    allNews = newsInput.*;
    my_total = allNews.length();

    for (var i:int = 0; i < my_total; i++) {

        my_url = allNews[i].url;
        my_title = allNews[i].title;
        my_date = allNews[i].date;

        var news_txt:TextField = new TextField();

        news_txt.text = my_date +" - "+ my_title;
        news_txt.autoSize = TextFieldAutoSize.LEFT;

        my_labels_array.push(news_txt);

        my_counter++;
    }

    if (my_counter == my_total) {

    addChild(my_newsTicker);
    my_newsTicker.addChild(my_labels_slides);


    nextNews();

    my_timer = new Timer(my_speed*1000);
    my_timer.addEventListener(TimerEvent.TIMER, timerListener);
    my_timer.start();
    }

}

function nextNews():void {
    var news_txt:TextField = TextField(my_labels_array[my_playback_counter]);
    my_labels_slides.addChild(news_txt);
    news_txt.x = (stage.stageWidth / 2)-(news_txt.width/2);
    news_txt.y = (stage.stageHeight / 2)-(news_txt.height/2);
    new Tween(news_txt,"alpha",Strong.easeOut,0,1,1,true);
}

function timerListener(e:TimerEvent):void {
    var news_txt:TextField = TextField(my_labels_slides.getChildAt(0));
    new Tween(news_txt,"alpha",Strong.easeOut,1,0,1,true);
    my_labels_slides.removeChildAt(0);

    my_playback_counter++;
    if (my_playback_counter == my_total) {
        my_playback_counter = 0;
    }
    nextNews();
} 

i testi si alternano correttamente ma non ho l'effetto dissolvenza
Grazie
Cinzia